Cancer is second only to cardiovascular disease as a cause of death in the United States. The American Cancer Society estimated that in 2004, there were 1.6 million new cases of cancer and 655,000 cancer-related deaths. There are currently over 10 million living Americans who have been diagnosed with cancer and the NIH estimates the direct medical costs of cancer as over $100 billion per year with an additional $100 billion in indirect costs due to lost productivity—the largest such costs of any major disease.
Cancer is a process by which the controlling mechanisms that regulate cell growth and differentiation are impaired, resulting in a failure to control cell turnover and growth. This lack of control causes a tumor to grow progressively, enlarging and occupying space in vital areas of the body. If the tumor invades surrounding tissue and is transported to distant sites, death of the individual can result.
The selective killing of cancer cells, while minimizing deleterious effects on normal cells, is a desired goal in cancer therapy. Modalities commonly used in the treatment of cancer include chemotherapy, radiation therapy, surgery and biological therapy (a broad category that includes gene-, protein- or cell-based treatments and immunotherapy). Despite the availability of a variety of anticancer agents, traditional chemotherapy has drawbacks. Many anticancer agents are toxic, and chemotherapy can cause significant, and often dangerous, side effects, including severe nausea, bone marrow depression, liver, heart and kidney damage, and immunosuppression. Additionally, many tumor cells eventually develop multi-drug resistance after being exposed to one or more anticancer agents. As such, single-agent chemotherapy is effective for only a very limited number of cancers. Many chemotherapeutic drugs are anti-proliferative agents, acting at different stages of the cell cycle. Since it is difficult to predict the pattern of sensitivity of a neoplastic cell population to anticancer drugs, or the current stage of the cell cycle that a cell happens to be in, it is common to use multi-drug regimens in the treatment of cancer.
Despite the significant research efforts and resources which have been directed towards the development of novel anticancer agents and improved methods for treating cancer there remains a need in the art for novel compounds, compositions, and methods that are useful for treating cancer with improved therapeutic indices.